Difference Between Spectrometer and Spectrophotometer

Intensive scientific research in different fields sometimes requires identifying compounds in living organisms, minerals, and perhaps the composition of stars. The chemically sensitive nature, difficulty of pure extraction, and distance make it almost impossible to identify the compounds properly in each case shown above by ordinary chemical analysis. Spectroscopy is a method to study and investigate materials using light and its properties.

Spectrometer

Spectrometer is an instrument used to measure and study the properties of light. It is also known as spectrograph or spectroscope. It is often used to identify materials in astronomy and chemistry by studying the light emitting from or reflected from the materials. Spectrometer was invented in 1924 by the German optical scientist Joseph von Fraunhofer.

The spectrometers of Fraunhofer design used a prism and a telescope to investigate properties of light. The light form the source (or material) passes through a collimator, which has a vertical slit. The light passing through the slit becomes parallel rays. Parallel beam of light emitting from the collimator is directed to a prism which separates different frequencies (resolves the spectrum), hence increase the ability to see minute changes in the visible spectrum. The light from the prism is observed through a telescope where magnification increases the visibility further more.

When looked through a spectrometer, the spectrum of light from a light source contains absorption and emission lines in the spectrum, which are identical to the specific transitions of the materials the light has passed through or the source material. This provides a method to determine unidentified materials by the study of the spectral lines. This process is known as the spectrometry.

Early spectrometers were extensively used in astronomy, where it provided the means of determining the composition of stars and other astronomical objects. In chemistry, it was used for identifying individual complex chemical compounds in materials which were difficult to isolate without changing its molecular structure.

Spectrophotometer

Spectrometers have developed into electronically operated complex machines, but they share the same principle as the initial spectrometers made by Fraunhofer. Modern spectrometers use a monochromatic light that passes through a liquid solution of the material and a photodetector detects the light. The changes of the light compared to the source light allow the instrument to output a graph of the absorbed frequencies. This graph indicates the characteristic transitions in the sample material. These types of advanced spectrometers are also called spectrophotometers because it is a spectrometer and photometer combined into a single device. The process is known as the spectrophotometry.

The advancement of the technology led to the adoption of spectroscopes into many science and technology fields. Extending beyond the frequencies of visible light, spectrometers capable of detecting IR and UV regions of the electromagnetic spectrums also were developed. Compounds with higher and lower energy transitions than the visible light can be detected by these spectrometers.

Spectrometer vs Spectrophotometer

• Spectroscopy is the study of methods of producing and analyzing spectra using spectrometers, spectroscopes, and spectrophotometers.

• The basic spectrometer developed by Joseph von Fraunhofer is an optical device that can be used to measure the properties of light. It has a graduated scale that allows the wavelengths of the specific emission/absorption lines to be determined by measuring the angles.

• Spectrophotometer is a development from the Spectrometer, where a spectrometer is combined with a photometer to read relative intensities in the spectrum, rather than the wavelengths of emission/absorption.

• Spectrometers were only used in the visible region of the EM spectrum, but spectrophotometer can detect IR, visible, and UV ranges.